Confocal microscopes of the species have been known for some time, and were described for the first time in U.S. Pat. No. 3,013,467 and implemented practically for the first time, for example, in DE 3 821 403 A1. In them, light that passes through a so-called Nipkow disk is used for point-like confocal illumination of a specimen. The light reflected from the specimen travels along the beam path of the microscope in the opposite direction, and the light passing through the Nipkow disk a second time an be detected or perceived by a detector or by the microscope operator's eye. The point-like pinholes of the Nipkow disk act as a confocal point light source and as confocal detection pinholes.
EP 727 684 A2 discloses a confocal optical scanner in which a Nipkow disk again implements confocal illumination and detection. Preceding the Nipkow disk provided therein, on the side facing toward the light source, is a collector disk having microlenses, which focuses the illuminating light of a light source onto the pinholes of the Nipkow disk. The quantity of light passing through the pinholes of the Nipkow disk can thereby be increased.
Confocal microscopes that comprise a confocal disk scanner are used in particular for real-time microscopy, since by rotation of the confocal disk scanner at high speed, confocal images of a specimen can be detected very quickly.
DE 44 37 896 C1 discloses a disk scanner for a confocal microscope in which both the light of a light source serving for illumination and the detected light coming from the specimen are reflected at the disk scanner. Here again, the reflective structures of the disk scanner act as confocal point light sources and detection pinholes.
DE 196 54 210 A1 discloses an optical arrangement for scanning a light beam with which confocal images can be scanned almost at video speed. A confocal microscope equipped with a scanning arrangement of this kind usually has illumination and/or detection pinholes that are responsible for the confocality.
Especially in microscopes having confocal disk scanners, only incident-light illumination, accomplished through the microscope objective, has heretofore been usual. Confocal transmitted-light illumination for the detection of transparent specimens is not readily possible. An illumination beam path that encompasses a light source and a first confocal disk scanner, which confocally illuminates the specimen from the side of the specimen plane facing away from the objective, could nevertheless be provided. For confocal detection, the light coming from the specimen would pass through the objective and a second confocal disk scanner, in which context the first disk scanner would need to rotate synchronously with the second disk scanner. This procedure is complex and difficult to align, and moreover requires a great deal of space.